A group of volunteers who traveled in the name of science have helped the researchers find out how LSD is confused with brain activity to cause a changed state of consciousness.
Scanning the brain to individuals with a high drug content reveals that the chemical allows parts of the bark to be flooded with signals that are usually filtered to prevent information overload.
The drug allows more information to flow from the thalamus, a kind of nervous janitor, to a region called the back of the tooth, and derives from the flow of information to another part known as the temporal cortex.
This interruption in communication can support some of the crash effect reported by LSD users from a sense of bliss and being one with the universe to hallucinations and what scientists in the field call "ego disintegration," where the feeling of self you are falling apart.
For the study, the researchers invited 25 healthy lab participants to be scanned under the influence of LSD and in another case after taking placebo. They were pre-screened around the scanner to make sure they feel comfortable coming inside when the drug stays up. If the machine suddenly turns into a threatening behavior, scanning may not have gone so well.
Scientists wanted to test the hypothesis presented more than a decade ago. It says that LSD causes the thalamus to stop filtering the information it is relaying to other parts of the brain. This is the destruction of this filter, which produces strange effects that the drug causes or thinks.
"The world around us is not the world we perceive because the thalamus filters out what it considers to be inappropriate information," says Catherine Prelair, project researcher at the Zurich University Psychiatric Hospital. "We do not necessarily perceive everything that we have, because it would be overloading information."
Scanning the volunteer's brain suggests that there may be some truth in the hypothesis. The LSD thalamus provides more information to some parts of the brain and suppresses information related to others. "What we've found is that the model is mostly true, but how information is distributed to the bark at LSD is much more specific than expected," says Preller.
It is not clear how confusing the flow of information in the brain gives rise to certain LSD-related sensations, but there are some hints from previous work. It is believed that, for example, the back of the dental cortex plays a role in shaping one's own sense of self, so overloading can cause self-indulgence.
LSD or lysergic acid diethylamide was first synthesized in 1938 and had a profound impact on psychology and psychiatric research in the 1950s and 1960s. While his admission as a recreational drug led to his ban, many scientists now suspect that it may be a powerful new weapon in the fight against depression and other mental disorders.
"We are approaching the understanding of the complexity of what is happening with LSD in the brain, and this is particularly important if we want to develop new drugs," says Preller. Recent research has been published in a collection of reports from the National Academy of Sciences.
The work follows a major study in 2016, which found that under the influence of LSD, the brain gains more visual areas than normal, enriching the images people see even when their eyes are closed. The study is the first to show how the brain looks like LSD on a modern scanner.